Degradation of trichloroacetic acid by an efficient Fenton/UV/TiO2 hybrid process and investigation of synergetic effect

An efficient hybrid degradation process combined Fenton with TiO2 photocatalytic oxidation for trichloroacetic acid (TCAA) was first investigated, and then the synergetic degradation effect between Fenton reagent and TiO2 photocatalytic oxidation was discussed in this study. The dominant factors, such as dosages of TiO2 and Fe2+, TCAA concentration and pH were researched and optimized. The cooperation effect between Fenton and TiO2 photocatalytic oxidation probably occurred because (1) more OH radicals were produced in the Fe(OH)2+ and H2O2 decomposition reactions irradiated by UV light; and (2) photoinduced electrons voluntarily participated in the reduction from Fe3+ to Fe2+, improving the efficient separation of the photogenerated electrons and holes. Adsorption and degradation were both involved in the removal of TCAA in this hybrid process, and the removal of TCAA followed the Langmuir model and the degradation kinetics accorded with first order degradation kinetics. Toxicity test using a bioluminescent bacterium Photobacterium phosphoreum as the indicator proved that the hybrid process was a safe treatment because the toxicity decreased greatly with the degradation time.